Purpose:To evaluate whether measurement of apparent diffusion coefficient (ADC) and pure diffusion coefficient (D) can help to characterize solid pancreatic masses. Materials and Methods:Diffusion-weighted MR imaging was performed in both a patient group (n ϭ 71; pancreatic cancer [n ϭ 47], mass-forming pancreatitis [n ϭ 13], solid pseudopapillary neoplasm [n ϭ 6], and neuroendocrine tumor [n ϭ 5]) and a normal control group (n ϭ 11) by applying three b-factors of 0, 500, and 1000 sec/mm 2 . ADC 500 , ADC 1000 , D (ADC using b ϭ 500 and 1000 sec/mm 2 ), and perfusion fraction (f, 1-exp [-500 sec/mm 2 ϫ (ADC 500 -D)]) of normal pancreas, pancreatic cancer, and mass-forming pancreatitis were compared using the Kruskal-Wallis test. Receiver operating characteristic (ROC) analysis was performed to evaluate the diagnostic performance and optimal cutoff value of these parameters in differentiating pancreatic cancer from mass-forming pancreatitis.Results: Normal pancreas had significantly higher mean ADC 500 , ADC 1000 , and f than either pancreatic cancer (P Ͻ 0.001, Ͻ 0.001, and 0.004, respectively) or mass-forming pancreatitis (P Ͻ 0.001, Ͻ 0.001, and 0.002, respectively). ADC 500 , ADC 1000 , and D of mass-forming pancreatitis were significantly lower than those of pancreatic cancer (P ϭ 0.002, 0.004, and 0.014, respectively). Sensitivities and specificities in the diagnosis of pancreatic cancer were 72.3% and 76.9% for ADC 500 , 87.2% and 69.2% for ADC 1000 , 87.2% and 61.5% for D, and 42.6% and 92.3% for f, respectively. Conclusion:Measurement of ADC and D may be helpful in differentiating pancreatic cancers from mass-forming pancreatitis.

Purpose:To assess the correlation between volumetric measurements of clot, semiquantitative clot burden indexes, and signs of right heart dysfunction at computed tomographic (CT) pulmonary angiography in patients with acute pulmonary embolism (PE) and to determine whether clot burden and signs of right heart dysfunction are associated with short-term mortality. Materials and Methods:This retrospective study was institutional review board approved and HIPAA compliant. CT pulmonary angiographic studies (January 2007 through December 2007) with findings positive for PE were retrieved. Two readers evaluated signs of right heart dysfunction at CT pulmonary angiography, measured clot volume using a dedicated software program, and assessed clot burden using semiquantitative scores (Qanadli and Mastora). Spearman rank coefficient was used to investigate correlation between clot burden measures and signs of right heart dysfunction. Uni-and multivariate analyses were used to test association between CT pulmonary angiographic findings and shortterm mortality. Results:A total of 635 CT pulmonary angiographic studies from 635 patients (304 men, 331 women; mean age, 59 years) were included; 39 (6%) patients died within 30 days. Clot volume was strongly correlated with Qanadli score (r = 0.841, P , .01) and Mastora score (r = 0.863, P , .01) and moderately correlated (r = 0.378, P , .01) with the ratio of right ventricle diameter to left ventricle diameter (RV/LV ratio). Among the pulmonary angiographic signs, only increase in RV/LV ratio (cut-off value, 1.0) was independently associated with short-term mortality in multivariate analysis. Conclusion:Clot volume strongly correlated with semiquantitative CT scores of clot burden, and greater clot volume was associated with higher incidence of right heart dilatation. Increase in RV/LV ratio was associated with short-term mortality; however, measures of clot burden were not.q RSNA, 2012 Supplemental material: http://radiology.rsna.org/lookup /suppl

Changes in ADCs of less than approximately 30% fall into the range of measurement error. Imaging technique significantly affected ADCs of malignant hepatic tumors. Lesion location and size are potentially influential on the reproducibility of ADC measurement.